Question

We say fossil fuels will last only for a few hundred years, comment.

Answer 1

A fossil fuel is a fuel that is formed by natural processes, such as anaerobic decomposition of buried dead organisms, and contains organic molecules derived from ancient photosynthesis that release energy during combustion. These organisms and the fossil fuels they produce have an average age of millions of years and in some cases more than 650 million years.

Complete answer:
Petroleum, coal, and natural gas are examples of fossil fuels that contain high levels of carbon. Kerosene and propane are two commonly used fossil fuel derivatives. Volatile materials with low carbon-to-hydrogen ratios (such as methane), liquids (such as petroleum), and nonvolatile materials composed of almost pure carbon, such as anthracite coal, are all examples of fossil fuels. Methane can be found in hydrocarbon fields alone, in conjunction with oil, or as methane clathrates.
The majority of air pollution deaths are caused by fossil fuel combustion products; it is estimated that this pollution costs more than 3% of global GDP and that phasing out fossil fuels would save 3.6 million lives each year.
The use of fossil fuels hurts the environment. The combustion of fossil fuels emits approximately 35 billion tonnes (35 gigatonnes) of carbon dioxide ($C{{O}_{2}}$) per year. Because natural processes can only absorb a small portion of that amount, there is a net increase in atmospheric carbon dioxide of many billions of tonnes per year.
$C{{O}_{2}}$ is a greenhouse gas that contributes to global warming and ocean acidification by increasing radiative forcing. To help reduce global greenhouse gas emissions, a global movement is underway to generate low-carbon sustainable energy. However, fossil fuels received a $320 billion subsidy in 2019.
Fossil fuels took millions of years for a dead organism to transform into petroleum, which is what fossil fuels are. Coal and natural gas are both sources of energy. Their reserves are scarce. Fossil fuels are used in a variety of ways. However, generation and reserves are only a few examples of where these are extracted. People are blindly relying on these fuels to power their daily lives.
Thus, say fossil fuels will last only for a few hundred years.

Note:
Because they can be burned (oxidized to carbon dioxide and water), fossil fuels produce significant amounts of energy per unit mass. Coal has been used as a fuel since before recorded history. Coal was used to power furnaces that smelted metal ore. While semi-solid hydrocarbons from seeps were also burned in antiquity, they were mostly used for waterproofing and embalming.